Small electronic imaging devices, such as cameras in cell phones and other small electronic devices, require zoom lens systems that are small in size, inexpensive to manufacture, and have exit pupils consistent with the requirements of the electronic sensor.
Conventional two-lens-group zoom lens systems have a negative first group that moves for compensation and focusing, and a positive second group that moves to effect a magnification change. They are sometimes referred to as np-type zoom lens systems.
While such np-type zoom lens systems are inexpensive, the leading negative group does not allow for compact size, and the positive group yields an exit pupil position too close to the image for the sensor to function properly. As a result, the current lens systems are larger than desired. Typically the first zooming group in such np-type zoom lens systems has included three or more separate lens elements and the second zooming group in such np-type zoom lens systems has included four or more separate lens elements, for a total lens element count of seven or more.
While other five-element zoom lens systems have been proposed, they are all believed to suffer from one or more of the drawbacks of large size, undesirable exit pupil position, insufficient zoom range.
It would be desirable to provide a zoom lens system design that is very inexpensive, is easly manufactured, has a sufficient zoom range and desirable exit pupil position, and is small enough and of sufficient optical quality/resolution to be used in small electronic cameras.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.